The present invention relates to an improvement of a sealing device for a linear guide which is used with machine tools, industrial machines, measuring apparatuses, and so forth.
A linear guide as shown in FIG. 6 is used generally. The linear guide provides: a guide rail 1 extended axially; and a slider 2 substantially U-shaped in section which is movably mounted over the guide rail 1. Two ball rolling grooves 3 are formed in each of the two side surfaces of the guide rail 1. The body 2A of the slider 2 (hereinafter referred to as "a slider body 2A", when applicable) has a pair of right and left wings, the inner surfaces of which have ball rolling grooves (not shown) which are confronted with the ball rolling grooves 3 of the guide rail 1, respectively. A number of rolling elements, namely, balls are rollingly provided in the spaces defined by those guide rails, so that the slider 2 is axially moved along the guide rail 1 through the rolling of the balls. Ball returning paths (not shown) are formed in the right and left wings of the slider body 2A in such a manner that they are axially extended through those wings. Two end caps 2B substantially U-shaped in section are attached to both end faces of the slider body 2, respectively. Each of the end caps 2B has curved paths (not shown) through which the above-described ball returning paths are communicated with said ball rolling grooves 3. That is, the curved paths, the ball returning paths, and the ball rolling grooves form endless ball circulating paths.
As the slider 2 moves along the guide rail 1, the balls between the guide rail 1 and the slider 2 advance in the ball rolling grooves to the one end portion of the slider body 2A, where they make U-turn being guided into the curved paths. Thereafter, the balls are moved through the ball returning paths to the other end portion of the slider body, where they make U-turn again being guided into the curved paths, thus returning into the ball rolling grooves. The above-described ball circulating operation is repeatedly carried out.
In FIG. 6, reference character denotes a grease nipple through which lubricant is supplied to the ball circulating paths in the slider 2.
If foreign matters such as dust and chips enter the gap between the guide rail 1 and the slider 2 slidably mounted over the former 1 and stick, for instance, to the ball rolling grooves, then they may obstruct the smooth rolling of the balls. In order to eliminate this difficulty, a pair of side seals 10 as shown in FIG. 7 are attached to the outer surfaces of the end caps 2B.
Each of the side seals 10 is formed by welding a seal member S of nitrile rubber or urethane rubber onto a reinforcing steel plate U-shaped in section. The side seals 10 are fastened to the end caps 2B at the front and rear ends of the slider 2 with bolts in such a manner that they are slidably in contact with the outer surface of the guide rail 1 to prevent the entrance of foreign matters into the slider 2 in front and in rear.
The above-described conventional sealing device for a linear guide is still disadvantageous in the following points:
(1) The sealing device formed by welding a sheet of nitrile rubber or urethane rubber to a steel plate is not self-lubricating. Therefore, the sealing device is allowed to slide smoothly by decreasing the friction between the sealing device and the guide rail with lubrication applied thereto from outside. Hence, in the case where the linear guide is used in the circumstance that foreign matter such as wooden pieces and casting chips sprinkle over it, that foreign matters, sticking to the sealing device, absorbs the lubricant, as a result of which the sealing device is quickly worn out, and at worst is broken.
(2) In the case where the linear guide is used in a clean room, in order to reduce the amount of dust produced while the linear guide is being used, a difficult and costly operation of applying a minimum quantity of lubricant required for rolling the balls to the ball circulating paths in the linear guide with an injector or a special injecting unit must be carried out.
(3) Furthermore, in the case where the linear guide is used in a clean room, the service life of the linear guide is ended when the minimum quantity of lubricant which has been injected thereinto during the assembling of the linear guide is used up.
(4) In addition, in the case where the linear guide is used in a clean room, in spite of the fact that the amount of lubrication supplied is small, the lubricant holding space is relatively large. Therefore, the lubricant thus supplied is not sufficiently applied to the ball circulating paths; that is, it is not effectively utilized.